The actuator expands and contracts by using a motor and a feed screw mechanism. A proposal has been made to provide a lock device for preventing inverse transfer of a driving force along a power transmission path connecting the motor and the feed screw mechanism together (see, for example, Japanese Unexamined Patent Application Publication No. 2009-173192).
FIG. 5 schematically illustrates a typical lock mechanism of a pin-insertion type using a solenoid. As illustrated in FIG. 5, a shift lock mechanism 100 using a solenoid is typically used in such a manner that a solenoid pin 101 is inserted in a groove 103 of a rotating body 102 so as to control the position of a counter part of the solenoid. In the case of using the shift lock mechanism 100 as a mechanism for locking the rotating body 102 such as a gear (not shown) of an actuator, a stroke of the actuator can be controlled by inserting the solenoid pin 101 into the groove 103 of the rotating body 102.
On the other hand, another type of such lock mechanism is a friction brake type mechanism in which an end surface of a pin is pressed against a rotating body to generate a frictional force so that the stroke can be controlled by using the frictional force. FIG. 6 schematically illustrates a typical lock mechanism of the friction brake type. As illustrated in FIG. 6, in a lock mechanism 110 of the friction brake type, a pin end surface 111a of a pin 111 is pressed against a rotating subject 112 with an appropriate spring force to generate a frictional force so that the stroke can be controlled by using the frictional force.